1. Field of the Invention
The present invention relates to a vapor compression cycle that includes an ejector, which serves as a depressurizing means for depressurizing fluid and which also serves as a momentum transporting pump for transporting the fluid by entraining action of discharged high velocity working fluid, so that such a vapor compression cycle is effectively applicable to, for example, a refrigeration cycle of a vehicle air conditioning and refrigerating system, which performs a passenger compartment cooling air conditioning operation and a refrigerator cooling operation through use of multiple evaporators.
2. Description of Related Art
Japanese Patent No. 1644707 discloses a vapor compression refrigeration cycle of FIG. 25, in which a portion of a refrigerant passage located downstream of a radiator 13 branches to two passages 51, 52. A cooling air conditioner evaporator 55 for cooling a vehicle passenger compartment is arranged in the passage 51, and a refrigerator evaporator 56 for cooling a refrigerator is arranged in the passage 52.
In the refrigeration cycle of Japanese Patent No. 1644707, the flow of the refrigerant is switched between the flow passage 51 for the passenger compartment cooling air conditioning operation and the flow passage 52 for the refrigerator cooling operation by switching solenoid valves 53, 54. In this way, the passenger compartment cooling air conditioning operation, which is performed through use of the cooling air conditioner evaporator 55, and the refrigerator cooling operation, which is performed through use of the refrigerator evaporator 56, are balanced.
Furthermore, with reference to FIG. 26, Japanese Patent No. 3322263 (corresponding to U.S. Pat. Nos. 6,477,857 and 6,574,987) discloses a vapor compression refrigeration cycle, in which an ejector 14 is used as a refrigerant depressurizing means and a refrigerant circulating means. In the vapor compression cycle, a first evaporator 61 is arranged between a refrigerant outlet of the ejector 14 and a gas-liquid separator 63, and a second evaporator 62 is arranged between a liquid refrigerant outlet of the gas-liquid separator 63 and a suction inlet 14c of the ejector 14.
In the vapor compression cycle of Japanese Patent No. 3322263 shown in FIG. 26, the pressure drop, which is induced by the high velocity flow of the refrigerant at the time of expansion of the refrigerant discharged from a nozzle portion 14a of the ejector 14, is used to draw the gas phase refrigerant, which is discharged from the second evaporator 62, through the suction inlet 14c of the ejector 14. Also, the velocity energy of the refrigerant, which is generated at the time of expansion of the refrigerant in the ejector 14, is converted into the pressure energy at a diffuser portion (a pressurizing portion) 14b to increase the pressure of the refrigerant, which is discharged from the ejector 14. Thus, the pressurized refrigerant is supplied to the compressor 12, and thereby the drive force for driving the compressor 12 can be reduced. Therefore, the operational efficiency of the cycle can be improved.
Furthermore, the two evaporators 61, 62 can be used to absorb heat from and thereby to cool a common space or can be used to absorb heat from and thereby to cool different spaces, respectively.
However, in the case of the refrigeration cycle of Japanese Patent No. 1644707 shown in FIG. 25, the flow passage 51, which is used for the passenger compartment cooling air conditioning operation, and the flow passage 52, which is used for refrigerator cooling operation, are switched through use of a timer. Thus, during the refrigerator cooling operation, the passenger compartment cooling operation cannot be performed, so that air conditioning feeling of the passenger may be deteriorated. Furthermore, due to a difference in the states of the evaporators 55, 56 after the switching operation, the discharged refrigerant temperature (i.e., the discharged refrigerant pressure) of the compressor 12 will change significantly. For example, in the case where the thermal load of the currently operated evaporator 55, 56 after the switching operation is relatively large, the compressor 12 could be operated at the maximum capacity to cause development of the abnormally high pressure in the high pressure side pipe line, which, in turn, could cause stop of the entire operation.
In the case of the vapor compression cycle of Japanese Patent No. 3322263 shown in FIG. 26, the compressor 12 should receive only the gas phase refrigerant, and the second evaporator 62 should receive only the liquid state refrigerant. Thus, the gas-liquid separator 63, which separates the refrigerant discharged from the ejector 14 into the gas phase refrigerant and the liquid phase refrigerant, is required. Therefore, the manufacturing costs are disadvantageously increased.
Furthermore, a distributing ratio of the refrigerant to the first evaporator 61 and to the second evaporator 62 needs to be determined using the single ejector 14 while maintaining the refrigerant circulating (gas phase refrigerant drawing) operation of the ejector 14. Thus, it is difficult to appropriately adjust the flow rates of the refrigerant of the first and second evaporators 61, 62.
Furthermore, the two evaporators 61, 62 can be used to absorb heat from and thereby to cool a common space or can be alternatively used to absorb heat from and thereby to cool different spaces, respectively. Also, it is recited that these two evaporators 61, 62 may be used to cool a room.
However, Japanese Patent No. 3322263 does not recite a specific arrangement of the two evaporators 61, 62 for cooling the room by the two evaporators 61, 62.
Furthermore, another previously proposed refrigeration cycle, which includes a plurality of evaporators, is shown in FIG. 27. FIG. 27 is a schematic diagram of the refrigeration cycle, which includes a previously proposed thermostatic expansion valve 105. In the refrigeration cycle, a refrigerant circulation passage R is divided into two passages R1, R2 at a point located on the downstream side of a radiator 102. One evaporator 104 is provided in the passage R1 and is used to perform, for example, passenger compartment cooling air conditioning operation. The other evaporator 106 is provided in the passage R2 and is used to perform, for example, refrigerator cooling operation.
In the case of the refrigeration cycle, which uses the multiple evaporators, such as of a vehicle air conditioning system including a cool box (the refrigerator), the evaporator 104 for the passenger compartment cooling air conditioning operation and the evaporator 106 for the refrigerator cooling operation are temperature controlled to the desired evaporation temperatures, respectively, by intermittently opening and closing a solenoid valve 107 arranged in the refrigerant passage R2 for the refrigerator cooling operation to supply the refrigerant to the refrigerant passage R1 for the passenger compartment cooling air conditioning operation. Furthermore, the thermostatic expansion valve 105 and a fixed metering device 108 are provided as a depressurizing means. In FIG. 27, numeral 101 indicates a refrigerant compressor, and numeral 109 indicates a check valve. FIG. 28 is a schematic diagram, in which a box type thermostatic expansion valve 105 is provided in the refrigeration cycle of FIG. 27.
In a case where an ejector is used in the refrigeration cycle of FIG. 28, adjustment (e.g., the flow rate adjustment) to correspond with the load changes and effective response to the rapid change in the rotational speed of the compressor are required. To achieve them, Japanese Unexamined Patent Publication No. 2004-44906 (U.S. patent application Publication No. 2004/0007014A1) discloses an ejector, which shows a high efficiency and a high responsibility throughout the entire load range.
However, for example, when the ejector of Japanese Unexamined Patent Publication No. 2004-44906 (U.S. patent application Publication No. 2004/0007014A1) is used in the refrigeration cycle of FIG. 28, which includes the box type thermostatic expansion valve 105, the orientation of the ejector is limited. Thus, there is less freedom in designing of the refrigeration cycle, i.e., the vapor compression cycle having the ejector.